Clothing firm Reiss has seen takings double since the Duchess of Cambridge began flashing her curves in its frocks.

Shoppers have swamped stores to get outfits Kate has sported on royal tours and visits.

The £159 cream silk dress she wore for her official engagement photos to Prince William, 29, sold at a rate of one a minute.

Reiss was prompted to relaunch the two- year-old Nanette dress, which then went on to sell out across the globe. Some were even selling on eBay for up to £750 in what retailers have dubbed the “Duchess effect”.

Experts say the 29-year-old Royal beauty’s style has made Reiss – one of Britain’s oldest clothes firms – “cooler and sexier.”

The “copy Kate” trend has rocketed its profits from £4.3million to £8.5million in the past 12 months.

The £175 Shola dress Kate wore when she met the Obamas at Buckingham Palace sold out online within an hour. And a £195 cream silk Peacock frock she donned for a day at the races was another instant hit.

It was the same story for almost every item she wore on her first royal tour to Canada.

And Reiss is not the only firm to benefit from her ability to mix High Street with designer gear.

Sales of Zara and Topshop dresses soared after Kate was seen wearing them.

A source said: “Kate is stylish and smart. She knows exactly what works and because she wears High Street clothes, normal women can copy her style and feel special too.”